Poly(chloro-p-xylylene) (PPXC) films with a thickness range encompassing more than three orders of magnitude (from 10 2 nm to 10 2 lm) were prepared on Si substrates by the chemical vapor deposition method under the same conditions. The effect of the film thickness (d) on the morphology, crystal structure, and crystal orientation behavior of the PPXC films was studied. The average roughness of the root mean square (rms) of the films increased with increasing d according to a power law (rms d b , where b is an exponent that depends on the film growth process over time and b 5 0.24060.005, as probed by atomic force microscopy), and the monomer diffusion and relaxation of polymer were suggested as the primary factors governing this morphological evolution. The X-ray diffraction results indicate that both the crystallinity and crystal size of PPXC increased with increasing d due to the surface confinement effect between the film and the substrate, which retarded the crystallization process. The X-ray pole figures suggested that the (020) fiber textures with the b axis parallel to the Si substrate normal existed in the PPXC films; these fiber textures, mainly composed of edge-on crystal lamellae, were thermodynamically favored. The Herman's orientation factor of the fiber textures increased gradually as d grew; this indicated that stronger (020) fiber textures with higher concentrations of edge-on lamellae existed in the thicker PPXC films. This thickness dependence of the crystal orientation behavior was interpreted to be caused by the strong adhesion between the polymer chains and the substrate.

Notched polymer-bonded explosive (PBX) structure is a mechanically weak link of a weapon system. In addition to the inherent brittleness and low strength of the PBX material, local stress concentration induced by a notch also threats the structural and functional integrity of a weapon system. In this study, a convenient strengthening method of local coating is newly adopted to the notched region of PBX beams. In virtue of a three-point bending test and digital image correlation measurement, the effects of local coating on strengthening and crack suppression of the beams are explored. Results demonstrate that, while relieving the stress concentration and improving the loadcarrying capability of the notched beams, the locally applied polymer coating can restrain the crack propagation in the PBX matrix, thus preventing the brittle fracture of the integral structure effectively. These explorations may provide significant inspiration for the potential application of local coating, and at the same time, lay foundation to the performance optimisation of energetic materials.

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Enhancing the mechanical properties is always an attractive challenge in the research area of energetic materials (EMs). In the present work, 1.5 wt.% MNsplasticizers (mononitrotoluene compounds, a mixture of 2-nitrotoluene and 4nitrotoluene) were applied for reinforcing a molten-energetic-composite (MEC) 2,4,6-trinitrotoluene (TNT)/1,3,5-trinitrohexahydro-1,3,5-triazine (RDX). Brazilian disk testing result shows that the tensile modulus of reinforced MEC increases by 26%. In order to explore the reinforcement mechanism, quantum chemistry (QC) and molecular dynamics (MD) simulation were performed to study the structural and physical properties of reinforced MEC. The basis set superposition error (BSSE) and the interaction energies of TNT, RDX and plasticizers were computed at MP2/6-311++G** levels. Compared with the weak interaction energy between RDX and TNT (−1.586 kJ/mol), the interaction energies of reinforced MEC increase massively after incorporating MNs-plasticizer. The SEM images of fractured surfaces from MECs also reveal that MNs can form layered deposits in TNT and closely surround RDX crystalline due to the presence of strong intermolecular-interaction. Besides, MD simulation results further explain that tensile modulus of (100) TNT and (100) RDX increases when introducing MNs plasticizer separately, which agree with the change trends of mechanical properties from the Brazilian disk test. This work provides a new path for studying reinforced energetic-composites by combining microscopy, mechanical test and theoretical simulations.